steep ‧ en /ˈstiːpən/ BrE AmE verb [intransitive and transitive]
[ Word Family: verb : ↑ steep , ↑ steepen ; noun : ↑ steepness ; adverb : ↑ steeply ; adjective : ↑ steep ]
if a slope, road etc steepens, or if something steepens it, it becomes steeper